(ABT 1830-)
| +---James Trethewy 
(ABT 1517-ABT 1573)
| +---Thomas Trethewy (-ABT 1616)
| +---Bartholomew Trethewy
| +---Bartholomew Trethewy (-1666)
| +---Thomas Trethewey (-ABT 1692)
| +---Bartholomew Trethewy (ABT 1667-MAY 1755)
| +---Walter Trethewy (ABT 1702-NOV 1751)
| | | +---Robert Trethewey (-JUL 1676)
| | | +---Walter Trethewey (-1710)
| | +---Elizabeth Trethewey (ABT 1670-AUG 1743)
| | +---Mary Brewer
| +---Humphrey Betty Trethewey (ABT 1731-JUL 1769)
| | +---Joan Woon (-1735)
| +---Thomas Trethewey (ABT 1758-25 FEB 1812)
| | | +---Richard Hendra
| | +---Blanche Hendra (ABT 1734-JAN 1775)
| | +---Jane Murton
+---Catherine Carvolth Trethewey (ABT 1805-06 JUN 1876)
+---Elizabeth Carvolth